1. Field of the Invention
The invention relates to a semiconductor device and a manufacturing method thereof, particularly, a back surface incident type semiconductor device having a light receiving element and a manufacturing method thereof.
2. Description of the Related Art
A semiconductor device detecting light coming from a main surface of a semiconductor die on the opposite side of a surface formed with a light receiving element has been conventionally known in a semiconductor device having a light receiving element. Such a semiconductor device is called a back surface incident type or back surface irradiation type semiconductor device. Next, a structure of the conventional back surface incident type semiconductor device will be described referring to figures. FIG. 10 is a cross-sectional view of the conventional semiconductor device.
A CCD (Charge Coupled Device) 211 as a light receiving element and its pad electrode 213 are formed on a front surface of a semiconductor die 210 as shown in FIG. 10. An opening 210H is formed on a back surface of the semiconductor die 210. Size of a bottom of the opening 210H is almost the same as that of the region formed with the CCD 211, forming a thin film portion 210T made of a thinned semiconductor die 210. The pad electrode 213 is electrically connected to an external connection electrode 217 formed on a supporting body 215 through a conductive bump 216. A space between the pad electrode 213 and the supporting body 215 is filled with resin 214.
The semiconductor die 210 is set in a package 219. A window member 220 made of glass or the like is provided on the package 219 on the side facing the opening 210H of the semiconductor die 210.
The external connection electrode 217 is connected to the package 219 through a bonding wire 218. In this semiconductor device, light coming from the window member 220 is detected by the CCD 211 through the thin film portion 210T of the semiconductor die 210.
In such a semiconductor device, since an electrode for reading a signal or a power supply wiring that is electrically connected to the CCD 211 does not exist on a light incident side (i.e. on the backside of the semiconductor die 210), light receiving efficiency can be enhanced compared with a design where light coming from the front surface of the semiconductor die 210 on which the CCD 211 is formed is detected. Furthermore, an energy beam such as an ultraviolet ray, a soft X-ray, or an electron beam, that is difficult to be detected when it passes through a thick semiconductor die, can be sensitively detected as much as possible. The relevant technology is disclosed in the Japanese Patent Application Publication No. hei 10-223873.
In a process of manufacturing the described conventional semiconductor device, a region of the semiconductor substrate corresponding to a region formed with the CCD 211 need be thinned, to a thickness of, for example, 10 to 20 μm by grinding. However, since it is very difficult to perform the grinding uniformly, the uniformity of the back surface of the thin film portion 210T thinned by the grinding is reduced. Therefore, light entering the thin film portion 210T is distorted to cause variation in imaging when the CCD receives light, that is, the CCD images. That is, a full performance of the semiconductor device is not guaranteed. Furthermore, since it costs much to partially thin such a semiconductor substrate, a manufacturing cost of the semiconductor device increases.
Furthermore, a mechanical strength of the thin film portion 210T of the semiconductor die 210 is low after the semiconductor device is completed. A connection strength of the bump 216 electrically connecting the semiconductor die 210 and the supporting body 215 is also low. Therefore, electrical connection between elements and electrodes is often insufficient, thereby lowering the performance of the semiconductor device.